The number of users in cellular systems has significantly increased. Accordingly, systems of 5th Generation have been increasingly demanded. Shifting from 4th Generation to 5th Generation demands some breakthroughs (e.g., improvement of both spectral efficiency and energy efficiency, and advanced radio frequency domain processing).
In cellular systems, scheduling of radio resources is performed for the purpose of avoiding interference between users, improving communication quality, and improving throughput. This scheduling has generally been performed every minimum transmission time interval (TTI), for example, in accordance with the communication environment at that time. Regarding this point, in long term evolution (LTE) and LTE-advanced (A), semi-persistent scheduling (SPS) has been standardized as a technology for scheduling radio resources in NPLs 1 and 2 below. SPS is a technology capable of allocating radio resources to user equipment (UE) at time intervals longer than one subframe. Note that the minimum TTI is 1 ms (one subframe) in LTE.
In terms of improving spectral efficiency, a multiple access technology (MAT) is an important element. As one of multiple access technologies, non-orthogonal multiple access (NOMA), such as interleave division multiple access (IDMA), has been attracting attention. Regarding IDMA, technologies related to interleaver allocation have been developed for the purpose of distinguishing between different users and effectively eliminating interference between the users to improve communication capability. For example, PTL 1 below discloses a technology of using different interleave patterns for different users or different cells to improve communication capability.